If climate change is real, why aren’t sea levels rising by much, and why aren’t those rises happening evenly across the globe?
Fact:
Sea levels are not even across the globe. Factors like winds, currents, river discharges, and variations in temperature and gravity make sea levels different in different parts of the world. It’s the same with sea level rises. For example, Sydney harbour has only risen by about 10 cm in the last century – about half the global average of 21 cm since 1880 – but in other places, like Micronesia, the sea level has risen by more the global average.
Worryingly, sea levels are rising at an increasing rate. For the first seven decades of the 20th century, they rose at an average of 1.3 millimetres per year. However, between 2006 and 2018, they rose at 3.7 millimetres per year – an increase of 185 percent.
In fact, we are only in the early stages of sea level rise. Around 400,000 years ago, when global temperatures were about 2°C warmer than the average for the past 8,000 years, sea levels were 6-9 metres higher than they are today. At current rates of warming, we are headed for a rise of up to one metre by the end of the 21st century. Some scientists believe the eventual rise will be as much as 3 metres. [It should be noted that tides are not uniform across the globe either. In some places, there is barely any difference between high tide and low tide at certain times of the year. In other places, such as the Bay of Fundy in Canada, the difference is as much as 16 metres!]
One city that is particularly threatened by sea level rise is New York, where levels have risen by 22 millimetres since 1950. The problem is being exacerbated by the fact that the city is sinking – at the rate of 1-2 millimetres a year, with some parts sinking at twice this rate. This is due to some of its skyscrapers having been built on sand and clay rather than solid rock. As a result, the city has faced two recent inundations – one in 2012 and the other in 2021 – when hurricanes caused whole areas to be flooded. These ‘once in a century’ events are now happening with alarming frequency. Other cities facing the threat of inundation include Miami, New Orleans, Shanghai, Jakarta, Bangkok, Lagos and Alexandria.
Global sea level rise, 1880-2020 [Source: Wikimedia Commons]